Oh, man, poor kid. I hope he heals quickly, but it makes 'em tough. I used to routinely flay open the front of by big toes when I was his age. Running without shoes on cement isn't the best thing for your skin lol. I still remember how uncomfy putting socks and shoes on was while healing.
Re: his short ach. tendons. I know this is probably a long shot and something that was ruled when you first started your journey into his condition, but have you all had a PT evaluate the ol' soleus/gastocnemius? Maybe they are really tight.